Another possibility is to put a "quick-reference" at the bottom of the input page. While this might make the server output an extra 100 characters per page created or updated, there might be a significant improvement due to people seeing the form they need, instead of imagining they don't need to go to the Formatting Tips.

added later: The pop-up is a good idea, daeve .... astounding that a pop-up window is EVER a good idea, isn't it?